Select, copy, and paste in automation track

it would be amazing if you could select, copy and paste in the automation track. it is also nice if you can place two points right under eachother. i think it becomes a sidechain dream.

**Below added by @Spekular**

A complete implementation of group selection in song editor should also allow deletion of the selected points.

Start by tracing the song editor's automation track and its handling of points. Define the scope for group selection, copying, pasting, placing vertically aligned points, and deleting selected points; done should cover these interactions consistently in the editor.

Written by the indexing model from the issue text.